In 2370, LieutenantWorf blindfolded EnsignSito Jaxa prior to subjecting to the Gik'tal, supposedly a test to allow her entrance into his advanced mok'bara class. Worf then told her to defend herself while he attacked, but after suffering several attacks, she removed the blindfold and labeled the test unfair. Worf told her that she passed, as the real objective was to bring home to her the lesson that "But perhaps the next time you are judged unfairly, it will not take so many bruises for you protest." (TNG: "Lower Decks")

Harry Kim sleeping with a mask

A special type of blindfold, also known as a mask, might be used to help sleeping. Harry Kim used such a mask. He picked up the habit out of necessity at the Academy as his roommate"never slept", but later continued it just because he had gotten used to it. He said it reminded him of being in the womb. (VOY: "The Cloud")